Periodontal diseases range from simple gum inflammation to serious disease that results in major damage to the soft tissue and bone that surround and support the teeth, ultimately resulting in tooth loss. The diseases are caused by bacterial colonization of the tooth surface, followed initially by a response of the innate immune system and manifest as gum inflammation (gingivitis). This gum inflammation then progresses to become periodontitis, in which the gums pull away from the teeth and form pockets in which the infection further thrives.
The innate immune response is followed by an adaptive immune response, in which antigen-presenting cells (mainly dendritic cells) accumulate in the gingiva and orchestrate a T cell response which in turn activates B cells to produce specific antibodies. CD4+ T cells have been shown to be the predominant population in adult periodontitis and, via recruitment and activation of osteoclasts function as a major source of bone loss. Thus, periodontal disease, while initially triggered by infection, is essentially an immunopathology, in which it is the immune response ensuing the infection that is responsible for the damage to tissue and bone.
Presently, the treatment of periodontal diseases consists primarily in eliminating the infection, mainly by mechanical removal of the plaque by scaling, debridement and root planing. The mechanical treatment can be supported by antimicrobial measures, such as mouth rinses or locally applied gels containing an antiseptic such as chlorhexidine. Tetracycline antibiotics (doxycycline, minocycline) are also used to combat the infection, either in form of locally applied preparations or in form of tablets. Tetracyclines act not only as antimicrobials but have in addition anti-inflammatory properties, which are poorly understood. Both minocycline and doxycycline have been shown to inhibit the release and the activity of matrix metallo proteinases (MMPs), a large group of enzymes that can be released from a variety of cells and are the main culprits of degrading tissue, cartilage and bone in many chronic inflammatory diseases, including periodontitis.
There is presently no treatment that addresses the events of the inflammatory response in a comprehensive way, notably its chronic manifestations, such that it would halt or reverse the tissue and bone destructive process. The drug compositions subject of this invention represent such a treatment.
Role of Cyclophilin in the Inflammatory Process
Cyclophilin was first discovered as binding protein of the immunosuppressant cyclosporin, normally resident within cells. The re-discovery of cyclophilin as intracellular peptidyl-prolyl cis-trans isomerase (PPIase) was reported several years later. Exposure of cells to inflammatory stimuli such as bacterial cell wall components (e.g. lipopolysaccharide, LPS) triggers cyclophilin to be secreted from cells into the extracellular space where it acts as a chemoattractant for inflammatory leukocytes. Leukocyte chemotaxis is mediated by a widely expressed membrane glycoprotein called CD147 or EMMPRIN (Extracellular Matrix Metallo Proteinase INducer) due to its ability to induce the production and release of MMPs from these cells. Both MMP release as well as leukocyte chemotaxis are triggered by the interaction between CD147 and cyclophilin, which occurs via the PPIase catalytic site which is also the cyclosporin binding site. Cyclosporin and other compounds that inhibit the PPIase catalytic activity of cyclophilin therefore block several key events involved in the bone and tissue destructive process of periodontal disease:
(1) They inhibit the infiltration of inflammatory leukocytes
(2) they inhibit the formation of antibody-secreting plasma cells resident in the gingiva
(3) they prevent the production and release of matrix metallo proteinases.
Cyclophilin inhibitors therefore represent a novel modality to treat the underlying mechanisms causing the immunopathology of periodontal disease.
Cyclosporin, when administered subcutaneously, has a positive effect on the formation of new alveolar bone (Toxicologic Pathology, Vol. 34(6), 2006, (Cetinkaya, Burcu Ozkan et al), “The effect of cyclosporin A on alveolar bone in rats subjected to experimental periodontal disease”, pages 716-722). The cyclosporin is administered as a subcutaneous injection. The effect on bone growth can only be seen using systemic treatment. The reference does not disclose formulations for topical applications into the inflamed gingival pocket to act as a localised anti-inflammatory agent.
It is known that induction of gingival overgrowth is a major undesired effect of systemic cyclosporin in transplant patients (Journal of Periodontology, Vol. 82(10), 2011, (Becerik, Sema et al), “Gingival crevicular fluid osteocalcin, N-terminal telopeptides, and calprotectin levels in cyclosporin A-induced gingival overgrowth”, pages 1490-1497). The side effect of gingival overgrowth is not unique to cyclosporin, other compound classes associated with gingival hyperplasia are anticonvulsants and calcium channel blockers, neither of which has anti-inflammatory activity. Gingival hyperplasia associated with all these medications consists of an excess deposit of extracellular matrix and is fundamentally different from physiological tissue, which consists primarily of cells (e.g. Kataoka et al., “Drug-induced gingival overgrowth—a review”, Biol Pharm Bull. 2005 October; 28(10):1817-21).
The undesired side effect of systemic treatment can be overcome by using localised topical formulations. Ongoing gingival inflammation, as seen in periodontitis, is a prerequisite of the onset of gingival overgrowth. Agents inhibiting the inflammatory processes of periodontitis could be expected to antagonise gingival overgrowth (Subramani et al., “The possible potential therapeutic targets for drug induced gingival overgrowth”, Mediators Inflamm. 2013). Gingival overgrowth induced by cyclosporin has been shown to be correlated with a certain threshold in cyclosporin blood levels (Webb et al., “Correlation between finger-prick and venous cyclosporin levels: association with gingival overgrowth and hypertrichosis”, Pediatr Nephrol. 2007 Dec. 22(12):2111; Thomas et al., “Risk factors in the development of cyclosporine-induced gingival overgrowth”, Transplantation. 2000 Feb. 27; 69(4):522-6).
However the topical treatments described herein will slow and/or stop the pathophysiology of chronic inflammation which must precede the physiological healing process, without causing the side effects induced by systemic treatment. It is the onset of the physiological healing process, that initiates the re-growth of physiological tissue, and the tissue which is formed by natural healing is fundamentally different from the overgrowth induced by cyclosporin and other drug classes.
DE 102008062373 describes the use of compounds known to induce gingival hypertrophy to fill the interdental gaps created by tissue erosion in periodontitis. There is no evidence of topical administration of any of the compounds mentioned in this document, nor is there any evidence of localised anti-inflammatory activity.
JPH0597697 describes the provision of an alveolar bone-regenerating agent containing cyclosporin A. The document lists a long list of possible compounds, including many that do not have any anti-inflammatory activity. There is no evidence of topical administration of cyclosporin A, nor is there any evidence of localised anti-inflammatory activity.
WO 03/033010 mentions periodontal disease as one condition among an exhaustive list of inflammatory and autoimmune diseases that can be treated with the compounds of WO 03/033010. This reference does not disclose any evidence supporting the claim that periodontal disease could be treated by cyclosporins. Evidence is given for inhibition of the Nuclear Factor of Activated T cells (NFAT), which is relevant for immunosuppression and for use of inhibitory compounds in transplantation. Furthermore, WO 03/033010 describes activity of compounds in test systems such as mixed lymphocyte reaction, plaque forming cell assay (Mishell-Dutton test), or delayed type hypersensitivity. All these test systems detect inhibitory activity of compounds on T cells (i.e. immunosuppressive activity). As outlined above, the role of cyclophilin in the inflammatory process of periodontitis is fundamentally different from that of immunosuppression.
The difference between immunosuppressive and anti-inflammatory activity is best illustrated by the fact that the well-known compound FK506 (Tacrolimus), is an immunosuppressant acting by a mechanism identical to that of cyclosporin but is not known to have anti-inflammatory activity (see e.g. Mattila et al., “The actions of cyclosporin A and FK506 suggest a novel step in the activation of T lymphocytes”, EMBO J. 1990 December; 9(13):4425-33; Liu J et al., “Calcineurin is a common target of cyclophilin-cyclosporin A and FKBP-FK506 complexes”, Cell. 1991 Aug. 23; 66(4):807-15).
WO 03/033010 A teaches that compounds can be administered by parenteral injection in the form of liquid dosage forms, be given by mouth (perorally) in the form of solid dosage forms, or be administered topically to the lung, eye, or vagina. However the document contains no evidence of topical administration of cyclosporin A, nor is there any evidence of localised anti-inflammatory activity.